Comparative assessment of analytical models for the ULS resistance verification of structural glass elements under variable loads

The design of glass structures, due to the intrinsic material properties, is mainly governed by the typical tensile brittle behavior of the material. In this regard, a currently open question related to the use of glass in buildings as a load-bearing constructional material, is represented by the correct estimation of static fatigue phenomena due to a generic combination of design actions. In this study, taking advantage of past literature contributions and existing design standards for glass, a novel analytical formulation is proposed for the resistance verification of a given structural glass elements under a Ultimate Limit State (ULS) combination of variable loads. The novel proposal is assessed towards three existing analytical formulations, based on two worked examples as well as an extended analytical analysis. In conclusion, the potential and criticisms of the examined approaches are discussed

Passive control systems for the blast enhancement of glazing curtain walls under explosive loads

Glass curtain walls are used in modern buildings as envelopes for wide surfaces due to a multitude of aspects. In glass curtain walls, tensile brittle panels are connected - through mechanical or adhesive joints - with steel frameworks or aluminum bracing systems, and due to the interaction of several structural components, the behaviour of the so assembled system is complex to predict, especially under exceptional loading conditions such as explosive events. In the paper, glazing curtain walls are investigated by means of Finite-Element (FE) numerical simulations, under the effect of air blast pressures of variable intensity. Their typical dynamic behaviour and criticalities under high-strain impact loads are first analyzed. By means of extended nonlinear dynamic FE parametric studies, innovative devices are applied to traditional curtain walls, at their support points, in order to improve their expected dynamic response. Two possible solutions, namely consisting of viscoelastic (VE) or elasto-plastic (PL) dampers, are proposed as passive control systems for the mitigation of maximum effects in the fa\ue7ade components deriving from the incoming blast pressures. As shown, although characterized by specific intrinsic mechanical behaviours, either VE or PL dampers can offer beneficial structural effects. In the first case, major advantages for the fa\ue7ade components derive from the additional flexibility and damping capacities of VE devices. In the latter case, PL dampers introduce additional plastic energy dissipation in the traditional curtain wall assembly, hence allowing preventing severe damage in the glazing components. It is thus expected that the current outcomes could represent a valid background for further experimental validation as well as detailed assessment and optimization of the proposed design concept

Dynamic response of cable-supported façades subjected to high-level air blast loads: numerical simulations and mitigation techniques

A glazing façade subjected to blast loads has a structural behaviour that strongly differs from the typical response of a glazing system subjected to ordinary loads. Consequently, sophisticated modelling techniques are required to identify correctly its criticalities. The paper investigates the behaviour of a cable-supported façade subjected to high-level blast loading. Nonlinear dynamic analyses are performed in ABAQUS/Explicit using a sophisticated FE-model (M01), calibrated to dynamic experimental and numerical results. The structural effects of the total design blast impulse, as well as only its positive phase, are analyzed. At the same time, the possible cracking of glass panels is taken into account, since this phenomenon could modify the response of the entire façade. Finally, deep investigations are dedicated to the bearing cables, since subjecting them to elevated axial forces and their collapse could compromise the integrity of the cladding wall. Based on results of previous studies, frictional devices differently applied at their ends are presented to improve the response of the façade under the impact of a high-level explosion. Structural effects of various solutions are highlighted through dynamic simulations. Single vertical devices, if appropriately calibrated, allow reducing significantly the axial forces in cables, and lightly the tensile stresses in glass panes

Correction to: TOSCA: a Tool for Optimisation in Structural and Civil engineering Analyses

With the aim of avoiding confusion with any other commercial software having the same name, any future reference to the optimisation software package described in this article should be made as TOSCA-TS

Mechanical analysis and characterization of IGUs with different silicone sealed spacer connections - Part 2: modelling

Insulated Glass Units (IGUs) typically consist of two glass layers, either monolithic and/or laminated sections, that mechanically interact via an hermetically-sealed air (or gas) cavity, and a series of linear spacer connections along their edges. In this paper, based on the experimental tests for small-scale IGU joints under pure shear and IGU prototypes in bending discussed in \u201cPart I\u201d, a special care is spent for the Finite Element (FE) numerical characterization and analysis of these composite systems, with a focus on the actual mechanical properties and load-bearing mechanism for the involved components. Major advantage is taken from the full 3D solid geometrical description of the connection components and the gas cavity infill. The actual role of both primary and secondary sealant layers is first assessed. Further support is derived from analytical calculations for the connection efficiency assessment, based on the adaptation of simplified formulations of literature. Finally, a calculation example is proposed to assess the magnitude of load sharing phenomena, based on FE numerical and analytical calculations for selected configurations

Enhancement of the seismic performance of multi-storey buildings by means of dissipative glazing curtain walls

Glazing facades are widely used in building structures, due to a series of aesthetic, thermal, lightening aspects. From a structural point of view, under the action of exceptional loads as impacts, explosions or seismic events, the glazing envelopes often represent the critical component for multi-storey buildings, due to the typically brittle behavior and limited tensile resistance of the glass panes, hence requiring specific design concepts. In this paper, the feasibility and potential of special mechanical connectors interposed at the interface between a given multi-storey primary building structure and the glazing facade are extensively investigated via accurate Finite-Element models, under the action of a set of seven natural seismic records. As shown, the proposed vibration control devices can markedly improve the dynamic performance of the traditional structure, both in terms of global (i.e. building seismic response) and local performances (i.e. at the component level). The final result, once the input parameters of the vibration control devices are properly designed, is an assembled structural system in which the glazing fa\ue7ade works as passive control system for the primary structure

Multiple dissipative devices for blast-resisting cable-supported glazing façades

The paper analyzes the structural response of a high-level air blast loaded cable-supported façade. Since the glass panels and the cables present a typical brittle behavior and are subjected to elevated tensile stresses when a high-level explosion occurs, multiple dissipative devices are simultaneously introduced in the conventional glazing system to mitigate the maximum effects of the design blast wave. Dynamic analyses are performed using a sophisticated FE-model to describe accurately the response of the façade equipped by dissipative devices. Based on numerical results of previous contributions, viscoelastic spider connectors (VESCs) are introduced in the points of connection between glass panels and pretensioned cables, to replace "rigid" spider connectors commonly used in practice. At the same time, rigid-plastic frictional devices (RPDs) are installed at the top of the bearing cables to mitigate furthermore the bracing system. As a result, due to the combined use of VESCs and RPDs opportunely calibrated, the maximum tensile stresses in the glass panels and in the cables appear strongly reduced. In addition, the proposed devices do not trouble the aesthetics of such transparent structural systems. At last, simple design rules are presented to predict the response of cable-supported façades subjected to high-level dynamic loads and to preliminary estimate the mechanical parameters of combined VESCs and RPDs

Dynamic Response of Cable-Supported Façades Subjected to High-Level Air Blast Loads: Numerical Simulations and Mitigation Techniques

A glazing façade subjected to blast loads has a structural behaviour that strongly differs from the typical response of a glazing system subjected to ordinary loads. Consequently, sophisticated modelling techniques are required to identify correctly its criticalities. The paper investigates the behaviour of a cable-supported façade subjected to high-level blast loading. Nonlinear dynamic analyses are performed in ABAQUS/Explicit using a sophisticated FE-model (M01), calibrated to dynamic experimental and numerical results. The structural effects of the total design blast impulse, as well as only its positive phase, are analyzed. At the same time, the possible cracking of glass panels is taken into account, since this phenomenon could modify the response of the entire façade. Finally, deep investigations are dedicated to the bearing cables, since subjecting them to elevated axial forces and their collapse could compromise the integrity of the cladding wall. Based on results of previous studies, frictional devices differently applied at their ends are presented to improve the response of the façade under the impact of a high-level explosion. Structural effects of various solutions are highlighted through dynamic simulations. Single vertical devices, if appropriately calibrated, allow reducing significantly the axial forces in cables, and lightly the tensile stresses in glass panes

Numerical assessment of vibration control systems for multi-hazard design and mitigation of glass curtain walls

Glass systems and facades are widely used in building structures, due to a multitude of aspects. Beside these motivations, from a pure structural point of view, glazing envelopes represent one of the most critical components for multi-storey buildings under the action of exceptional loads as impacts, explosions, seismic events or hazards in general. Such systems represent in fact the first line of defense from outside. Given the current lack of specific design regulations for the mitigation and enhancement of glass curtains under extreme loads, as well as the typically brittle behaviour and limited tensile resistance of glass as material for constructions, the same facades require specific, fail-safe design concepts. In this paper, the feasibility and potential of special mechanical connectors interposed at the interface between a multi-storey primary building structure and the enclosing glazing facade are investigated via accurate Finite-Element (FE) numerical models, under various impact scenarios. At the current stage of research, careful consideration is given both to the observed global performances as well as to local mechanisms, based on computationally efficient FE models inclusive of damage models to account for failure mechanisms in each system component. Compared to earlier research efforts, the attention is focused on the multi-hazard performance of a given case study building, subjected to extreme loadings such as seismic loads or blast events. As shown, even the typically different features of the examined loading conditions, when the proposed vibration control devices are properly designed and the curtain wall is considered as part of a full 3D building, the final result is an overall assembled structural system in which the glazing facade can work as a passive control system for the building system, in the form of a distributed Tuned-Mass Damper (TMD), with marked benefits in terms of protection level as well as design optimization

Structural assessment and lateral\u2013torsional buckling design of glass beams restrained by continuous sealant joints

Glass is largely used in practice as a structural material, e.g. as beam and plate elements able to carry loads. Their structural interaction is often provided by mechanical connections, although recent trends are moving toward the minimization of metal components and the primary involvement of adhesives or silicone structural joints working as partially rigid continuous restraints. In this work, the lateral\u2013torsional buckling (LTB) behavior of glass beams laterally restrained by continuous silicone joints is assessed. Based on earlier contributions of literature and extended parametric Finite-Element (FE) numerical investigations, closed-form solutions are suggested for the estimation of their Euler\u2019s critical buckling moment under various loading conditions. Finally, by means of more detailed incremental nonlinear analyses, their global LTB response is also investigated, to assess their sensitivity to initial geometrical imperfections as well as their prevalent LTB failure mechanism. In conclusion, a generalized buckling design curve able to account for the structural contribution provided by structural silicone joints is proposed for a rational and conservative LTB verification